
where \({\hat{g}}({\mathbf {k}_{\rm F}},{\omega _{m}},{\mathbf {r}})\)  is the quasi-classical Green's function in a \(2\times 2\)  matrix form.
[1]}, [2]}
The \({\mathbf {k}_{\rm F}}\)  dependence in \(\Delta _1({\mathbf {k}_{\rm F}},{\omega _{m}},{\mathbf {r}})\)  and \(\Delta _2({\mathbf {k}_{\rm F}},{\omega _{m}},{\mathbf {r}})\) 
represents the orbital symmetry of the order parameter,
while \({\mathbf {r}}\)  in Eq. (REF ) represents the center of mass coordinate of the Cooper pair.
The \({\omega _{m}}\)  dependence in the order parameter is owing to the odd-frequency component.
